With the continuous development of mobile communication technology, a variety of different communication systems have emerged constantly. A development trend of an existing communication system is a long term evolution (Long Term Evolution, LTE) system, an LTE technology mainly supports high speed data transmission based on an orthogonal frequency division multiple access (Orthogonal Frequency Division Multiple Access, OFDMA) technology and a multiple-input multiple-out-put (Multiple-Input Multiple-Out-put, MIMO) technology. The two technologies have advantages unmatched by other technologies on such aspects as improving data transmission, improving spectrum efficiency and the like, and can exponentially improve the capacity and spectrum efficiency of the communication system without increasing the bandwidth, thus becoming key technologies of the next generation of wireless transmission systems.
Furthermore, with the in-depth study of a multi-antenna technology, the communication system has been expanded from a point-to-point single-user system to a point-to-multipoint multiuser system. In the LTE system, a multi-antenna multiplexing gain is generally achieved by the MIMO technology pre-coded by a sending end, in order to expand the multiuser channel capacity area. The information of a plurality of users may be transmitted on the same time, frequency domain and code domain resources by adopting a spatial division multiple access (Spatial Division Multiple Access, SDMA) technology on the basis of the MIMO technology pre-coded by the sending end, thus compared with a single-user MIMO system, the system capacity and the spectrum efficiency thereof may be greatly improved.
Enhanced downlink MIMO is one of the key technologies of LTE, but the technology still has some problems influencing the multiuser MIMO performance at present, for example, the maximum number of multiplexed streams is merely 4 (i.e., multiplexing of at most 4 users is supported), and the maximum number of multiplexed streams of each user is 2.